test/ceph-helpers: Pass timeout and add timeout for commands in test_pg_scrub
In test_pg_scrub, after killing an OSD, subsequent pg_scrub checks and calls to flush_pg_stats
can hang or timeout with the default time because the OSD is no longer running.
This was causing test failures.
This fix addresses two issues:
1. test_pg_scrub: Explicitly pass the WAIT_FOR_CLEAN_TIMEOUT and TIMEOUT variables (both set to 2)
to the pg_scrub call after the OSD is killed. This prevents a hang in the wait_for_clean
check within pg_scrub.
2. flush_pg_stats: Add an explicit timeout to the ceph tell osd.$osd flush_pg_stats command,
allowing it to fail quickly when an OSD is unresponsive.